Re: question about HDF5 parallel use of unlimited dimensions...

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On Thu, 30 Jun 2005, Ed Hartnett wrote:

> As I understand it, using fixed-length data, my different processes
> could write their data and go on their merry way, without waiting for
> anything.

This can be done only if you know that the different processors are
not updating the same chunk.

Fixed vs extended is not relevant to the basic issue: you must
coordinate all writes in parallel.
> As currently implemented, H5Dextend is called when needed as you write
> the data in netcdf. That is, if you are writing a record at a time,
> H5Dextend is called for each record.

This will be quite slow in parallel. But it will work.

Presumably, user's can control this by batching the writes.

Robert E. McGrath
National Center for Supercomputing Applications
University of Illinois, Urbana-Champaign
Champaign, Illinois 61820


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